Double-plate rotary barrel pump

ABSTRACT

The present invention relates to a rotary barrel pump (6) comprising two plates: a mobile plate (2) also driven by drive shaft (5) and a variable-inclination plate (7), the two plates (2, 7) being linked to one another by a pivot connection.

FIELD OF THE INVENTION

The present invention relates to the field of pumps, in particular forhigh-pressure pumping, notably for drilling operations.

BACKGROUND OF THE INVENTION

Today, crankshaft drive pumps are the most widely used across allindustry sectors: capital goods, oil, gas and food industries,automotive industry, building industry (heating, wells, airconditioning, water pumps, etc.), and more specifically for water andwaste treatment (water network and wastewater system). However, they arestill manufactured on the basis of designs dating from the 1930 s, andvery few research and development surveys have been carried out toimprove their performances, reduce their cost price, minimize theirmaintenance costs or decrease their environmental footprint. These pumpshave limits in terms of power, pressure/flow rate torque (i.e. limitsresulting in pressure surge type phenomena generated by the sinusoidalresponse of the pressure produced by the crankshaft), weight, efficiencyand service life. Furthermore, they do not allow to have a variabledisplacement and they therefore lack flexibility in use.

Besides, in the field of hydrocarbon production, it is currentlyobserved that wellbores need to reach increasingly great depths, whichinvolves working at increasingly high injection pressures. Oil companiestherefore need ultra-high pressure pumps to reach the required depthsfor drilling mud injection for example. These pumps must also bereliable, economical, flexible and compact, so as to meet the ever moredemanding requirements of the energy sector.

Another positive-displacement pump technology is the barrel pump. It ismainly intended for pumping at lower pressure and flow rate (it ismainly used for pumping hydraulic oils) and it has many advantages:

-   -   excellent weight/power ratio    -   very good price/performance ratio    -   interesting mechanical and volumetric efficiencies    -   variable displacement capacity through plate inclination        adjustment.

Pumps designed with a barrel operate by means of a rotary plate systemthat actuates the various pistons one after another. When a piston is inan intake phase, the opposite piston is in delivery mode, which providesa constant flow upstream and downstream from the pump. The distributionof the piston positions guided by the barrel provides progressivedistribution of the forces upon rotation of the shaft driven by themotor.

There are three main barrel pump architectures:

-   -   stationary barrel pumps (FIG. 1): in this configuration of pump        1, where the barrel is stationary, it is inclined plate 2 that        rotates (driven by shaft 5) so as to generate the motion of        pistons 3 in their sleeves 4 (compression chamber). The link        between pistons 3 and plate 2 is then provided by ball joint        pads that rub on plate 2. The advantage here is a very low        inertia of the rotating parts. However, this configuration makes        it difficult to have a variable displacement. Furthermore, in        case of high pressures and flow rates, the friction forces        between the plate and the pads are not negligible and make it        difficult, or even impossible, to produce the pump;    -   swash-plate barrel pumps: the barrel is stationary in this        architecture and there are two plates, a first inclined plate        rotates and transmits to the second plate only the oscillating        motion. Thus, the pistons can be linked to the second plate, the        swash plate, without friction members being required, for        example with a connecting rod linked to the piston and to the        plate by spherical joints. This architecture is suited to        high-pressure pumping due to the absence of friction elements        (some can be found on the geothermal energy market). It also        provides an excellent mechanical efficiency. This configuration        makes it possible to produce a variable displacement, which        however remains difficult to integrate and to design;    -   rotary barrel pumps (FIG. 2): within pump 1, it is plate 2 that        is stationary and barrel 6 carrying pistons 3 rotates, which        provides motion of pistons 3 in their sleeves 4 (compression        chamber). The link between piston 3 and plate 2 is provided in        the same manner as for the first configuration. The advantage of        this architecture is that the plate can be readily adjusted in        inclination, which makes it possible to have a variable        displacement. On the other hand, the inertia of the rotating        parts increases in a quite significant manner since the barrel        and all of the pistons are rotated. Furthermore, for this        configuration, significant friction occurs between the plate and        the rods connected to the pistons, which generates efficiency        loss.

In order to overcome these drawbacks, the present invention relates to arotary barrel pump comprising two plates: a mobile plate also driven bythe drive shaft and a variable-inclination plate, the two plates beinglinked to one another by a pivot connection. Thus, the drive of themobile plate by the drive shaft allows contact between two rotatingparts: the rods and the mobile plate, thereby limiting friction lossesbetween these parts. The variable inclination enables variabledisplacement of the pump.

SUMMARY OF THE INVENTION

The invention relates to a barrel pump comprising a casing andcomprising, within said casing:

-   -   a drive shaft,    -   a cylinder block comprising at least two circumferentially        distributed compression chambers, said cylinder block being        driven by said drive shaft,    -   a mobile plate,    -   at least two pistons in translation respectively in said        compression chambers of said cylinder block, said pistons being        driven by said mobile plate by means of connecting rods.

Said mobile plate is driven by said drive shaft and said barrel pumpcomprises a plate with variable inclination relative to said driveshaft, said mobile plate being in pivot connection relative to saidvariable-inclination plate around the axis of said variable-inclinationplate.

According to one embodiment of the invention, said pivot connectionbetween said mobile plate and said variable-inclination plate consistsof means for supporting the loads and means for holding up the assemblyof the two plates.

Advantageously, said pivot connection between said mobile plate and saidvariable-inclination plate consists of a conical roller thrust and aball bearing.

Preferably, said conical roller thrust is arranged between an outershoulder of said mobile plate and an inner shoulder of saidvariable-inclination plate.

Advantageously, said ball bearing is arranged between an outer shoulderof said mobile plate and an inner shoulder of said variable-inclinationplate.

According to an embodiment, said mobile plate is driven by said driveshaft through a pin spherical joint.

According to one aspect, said pin spherical joint comprises a device forforming a pin spherical joint in form of a hollow revolution partcomprising a substantially cylindrical inner surface and an outersurface having substantially the shape of a truncated sphere at bothends, said inner surface comprises at least one groove or one femalespline, and said outer surface comprises at least one crowned spline.

Advantageously, the device for forming a pin spherical joint is mountedon said drive shaft by means of a key or a splined shaft, and saidmobile plate is mounted on said device by means of at least one groovecooperating with said at least one crowned (or domed) spline.

Preferably, said mobile plate comprises a partly spherical innersurface. According to an implementation of the invention, said barrelpump comprises a means for controlling the inclination of saidvariable-inclination plate.

Advantageously, said inclination control means comprises a worm drivesystem.

Preferably, said rods are connected to said mobile plate withoutfriction pads.

Furthermore, the invention relates to the use of said barrel pumpaccording to one of the above features for a drilling operation, inparticular for injecting drilling mud into a wellbore.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the device according to the inventionwill be clear from reading the description hereafter of embodimentsgiven by way of non-limitative example, with reference to theaccompanying drawings wherein:

FIG. 1, already described, illustrates a stationary barrel pumpaccording to the prior art,

FIG. 2, already described, illustrates a rotary barrel pump according tothe prior art,

FIG. 3 illustrates a barrel pump according to an embodiment of theinvention,

FIG. 4 illustrates a device for forming a pin spherical joint linknecessary for rotation and inclination of the mobile plate according toan embodiment of the invention, and

FIG. 5 illustrates the pivot connection between the mobile plate and thevariable-inclination plate according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a rotary barrel pump. The purpose ofthe barrel pump is to pump a fluid (for example water, oil, gas,drilling mud, etc.) through linear displacement of several pistons. Thistype of pump affords the advantage of being compact, of havinginteresting mechanical and volumetric efficiencies, as well as anexcellent weight/power ratio. Furthermore, rotary barrel pumps aresuited for high-pressure pumping.

The barrel pump according to the invention comprises a casing and itcomprises within the casing:

-   -   a drive shaft driven in rotation relative to the casing by an        external energy source, notably a prime mover (thermal or        electric for example), in particular by means of a transmission        (a gearbox for example),    -   a mobile (rotary) plate driven by the drive shaft: the mobile        plate is driven in relation to the drive shaft, the plate is        therefore rotary, furthermore the mobile plate is inclined        relative to the drive shaft,    -   a cylinder block (referred to as barrel) comprising at least two        circumferentially distributed (in other words, arranged in a        circle) compression chambers (also referred to as sleeves), the        cylinder block is rotary and driven by the drive shaft,    -   at least two pistons in translation respectively in the        compression chambers, the pistons are driven by the mobile plate        by means of connecting rods (the rods connect, through the        agency of spherical joints, the mobile plate and the pistons so        as to convert the motion of the mobile plate to a translational        motion of the pistons), and the translation of the pistons        within the compression chambers generates pumping of the fluid,        and    -   a plate with variable inclination relative to the drive shaft,        apart from the adjustment of the inclination thereof, this plate        is stationary relative to the casing, and the mobile plate is in        pivot connection relative to the variable-inclination plate        about the axis of the variable-inclination plate (this axis        corresponds to a normal direction to the plate and it can        correspond to the axis of revolution of the variable-inclination        plate when the plate has the shape of a disc), thus the        inclination of the mobile plate is identical to the inclination        of the variable-inclination plate.

The variable inclination of the variable-inclination plate allows tohave a variable displacement of the pump, by modifying the stroke of thepistons.

Advantageously, the spherical joints between the connecting rods and themobile plate are provided without friction pads (there is no frictionconnection between the rods and the mobile plate), which is madepossible by the mobile plate. Indeed, one of the specific features ofthe invention is based on the double plate design and, morespecifically, on the connection of the mobile plate with thevariable-inclination plate and its drive via the power input shaft. Mostplate pumps present on the market are intended for lower flow rate andpressure activities, and the mechanical stresses on the various pumpcomponents are therefore more limited. Within the context of a high flowrate and high pressure use of these pumps available on the market, themechanical stresses involved are significant and friction pads aretherefore essential for these pumps. Furthermore, the design of frictionpads between the rods and the inclined plate becomes critical, inaddition to reducing the final efficiency of the pump by a few points.The design of a double plate, one stationary and the other rotary, thusallows an increase in the final efficiency of the pump, without frictionpads, and enables the pump to be used under high flow rate and highpressure conditions.

According to an embodiment of the invention, the pivot connectionbetween the mobile plate and the variable-inclination plate can consistof means for supporting the loads and means for holding up the assemblyof the two plates. For example, this pivot connection can be made up ofa conical roller thrust and of a ball bearing. The conical roller thrustis capable of withstanding the axial and radial loads exerted on theplates, and the ball bearing allows to hold up the assembly of the twoplates (mobile and variable-inclination plate).

According to an aspect of this embodiment, the mobile plate can comprisetwo outer shoulders for the arrangement of the conical roller thrust andthe ball bearing. The shoulder with the smaller diameter can be intendedto receive the conical roller thrust and it can be arranged on the sideof the mobile plate remote from the connecting rods. Furthermore, theshoulder with the larger diameter can be intended to receive the ballbearing and it can be arranged near the side of the mobile plate closeto the rods.

Besides, the variable-inclination plate can comprise two inner shouldersfor the arrangement of the conical roller thrust and the ball bearing.The shoulder with the smaller diameter can be intended to receive theconical roller thrust and it can be arranged near the center of thevariable-inclination plate. Furthermore, the shoulder with the largerdiameter can be intended to receive the ball bearing and it can bearranged on the side of the variable-inclination plate close to themobile plate.

This arrangement of the conical roller thrust and the ball bearing withthe inner and outer shoulders provides a simple assembly of the twoplates.

According to an implementation of the invention, the mobile plate can bedriven by the drive shaft through a pin spherical joint. A pin sphericaljoint is a link between two mechanical elements with four degrees ofconnection and two degrees of relative movement; only two relativerotations are possible, the three translations and the last rotationbeing linked. It is generally a spherical joint provided with a pinhindering rotation. The operating principle of this type of linkconsists in providing torque transmission between two rotatingassemblies whose axes are not colinear.

The pin spherical joint allows to synchronize the rotation of the mobileplate and of the cylinder block (barrel).

According to an aspect of this implementation of the invention, the pinspherical joint can consist of a specific device for forming a pinspherical joint. The device for forming the pin spherical joint can be ahollow revolution part. It is reminded that, in geometry, a revolutionpart is a part generated by a closed plane surface rotating about anaxis located in the same plane and having no point in common therewith,or only boundary points.

For clarity of the description, the term “device” is used in the rest ofthe description below to designate the specific device for forming a pinspherical joint.

The device for forming the pin spherical joint comprises a substantiallycylindrical inner surface. Thus, the hollow part of the device issubstantially cylindrical. The device is therefore suited to be mountedon a cylindrical shaft. The inner surface comprises at least one groovefor inserting a key or at least one female spline for inserting asplined shaft, so as to transmit the torque between a shaft and thedevice. Using a key or spline transmission enables high torquetransmission.

The device according to the invention comprises an outer surface havingsubstantially the shape of a truncated sphere at both ends. The sphereis truncated by two planes perpendicular to the axis of revolution ofthe device. This partly spherical shape of the outer surface provides aspherical joint. Furthermore, the outer surface comprises at least onecrowned (or domed) spline. The crowned spline allows, on the one hand,to form the pin of the pin spherical joint and, on the other hand, toprovide large torque transmission between the device and an elementpositioned on the outer surface of the device (a plate or a disc forexample).

This design of the device for forming a pin spherical joint provideshigh compactness, large angular displacement and simplicity of use.

Advantageously, the groove(s) and the spline(s) are parallel to the axisof revolution of the device.

Preferably, the spline(s) of the outer surface have a crowned (or domed)shape parallel to the globally spherical shape of the outer surface ofthe device. Thus, the splines may be involute splines (splines which aredeveloped along a circle) so as to have the greatest transmissibletorque.

According to an aspect of this embodiment of the invention, the outersurface comprises a plurality of crowned splines evenly distributed overthe circumference of the spherical surface. A higher torque can thus betransmitted between the device according to the invention and theelement positioned on the outer surface of the device. The splines arepreferably parallel to one another. For example, the outer surface ofthe device can comprise between five and nineteen crowned splines,preferably between seven and thirteen, in order to optimize themanufacture of the device and the torque transmissible thereby, and tooptimize the distribution of forces in the splines.

Thus, for the pin spherical joint link between the drive shaft and themobile plate, the device for forming a pin spherical joint is mounted onthe drive shaft by means of at least one key or by means of a splinedshaft. Furthermore, the mobile plate is mounted on the outer surface ofthe device so as to form a pin spherical joint link by means of at leastone crowned groove (female spline) cooperating with the crownedspline(s).

With the invention, a pin spherical joint link is formed between thedrive shaft and the mobile plate: the mobile plate can rotate by meansof the spherical outer surface of the device, and the torque can betransmitted from the shaft to the plate by the key or the splines of thedrive shaft or by the crowned spline(s).

This link is here a non-slip constant-velocity spherical joint, whichmeans that the rotational speed at the joint input is identical to therotational speed at the joint output, and this connection occurs withoutslip but through direct mechanical drive.

This design of the connection enables a pin spherical joint linkproviding high compactness, large angular displacement and simplicity ofuse.

To achieve the pin spherical joint link, the mobile plate can comprise asubstantially spherical inner surface provided with female splines.

In order to facilitate assembly of the connection, the mobile plate canconsist of two half-shells. Alternatively, the mobile plate can be madeof a single piece.

According to an aspect of the invention, the mobile plate can comprise ameans forming an angular stop. It can be a surface coming into contactwith the shaft; for example, the plate can comprise a conical innersurface coming into contact with the shaft for the maximum angulardisplacement.

Alternatively to this embodiment of the pin spherical ball joint, thespherical joint link can be a ball joint bearing.

The plates can have substantially the shape of a disc. However, theplates may have any shape. Only the compression chambers (and thepistons) are arranged in a circle.

Advantageously, the pump according to the invention can comprise anumber of pistons ranging between three and fifteen, preferably betweenfive and eleven. Thus, a large number of pistons provide a continuousflow upstream and downstream from the pump.

Conventionally, the pump further comprises an inlet and an outlet forthe fluid to be pumped. The fluid passes through the pump inlet, flowsinto a compression chamber, where it is compressed, then it isdischarged from the pump through the outlet by means of the piston.

According to an embodiment of the invention, the angle of inclination ofthe variable-inclination plate relative to the axial direction of thedrive shaft can range between 70° and 90°. In other words, thevariable-inclination plate (and a fortiori the rotary plate) can beinclined at an angle ranging between 0° and 20° to a radial direction ofthe drive shaft.

According to an implementation of the invention, the barrel pump cancomprise a means for controlling the inclination of thevariable-inclination plate. For example, this control means can comprisea worm drive system.

According to an aspect of the invention, the barrel can be made of twoparts, a first part being intended for guiding, and the second partbeing intended for sealing.

FIG. 3 schematically illustrates, by way of non-limitative example, akinematic diagram of a rotary barrel pump according to an embodiment ofthe invention. Rotary barrel pump 1 comprises a drive shaft 5. Therotation of drive shaft 5 is performed by an external source, not shown,an electric machine and a gearbox for example. Drive shaft 5 rotateswith respect to casing 15. Furthermore, drive shaft 5 rotationallydrives barrel 6 that comprises compression chambers 4.

Drive shaft 5 also drives a mobile plate 2 by means of a pin sphericaljoint 9.

Pump 1 further comprises a variable-inclination plate 7 which, exceptfor the inclination adjustment thereof, is stationary relative to casing15. The means for adjusting the inclination of variable-inclinationplate 7 is not shown.

Mobile plate 2 is in pivot connection with respect tovariable-inclination plate 7 about the axis of variable-inclinationplate 7.

Pump 1 comprises a piston 3 driven by a translational motion(reciprocating motion) within a compression chamber 4.

The reciprocating motion of piston 3 is achieved by means of a rod 8connecting mobile plate 2 and piston 3 by means of spherical joints.This reciprocating motion of piston 3 within compression chamber 4allows the fluid to be pumped.

FIG. 4 schematically illustrates, by way of non-limitative example, adevice for forming a pin spherical joint link according to an embodimentof the invention. Device 10 is a revolution part rotating about axis XX.Device 10 is hollow and it comprises a cylindrical inner surface 11.Inner surface 11 comprises a groove 14. The section of groove 14 issubstantially rectangular. Device 10 comprises an outer surface 12having substantially the shape of a truncated sphere at both ends, thetruncation being achieved at two planes perpendicular to axis XX. Outersurface 12 comprises a plurality of crowned (or domed) splines 13, inthe case illustrated here, nine crowned splines 13. Crowned splines 13have an outer surface substantially parallel to outer surface 12 of thedevice. These splines 13 are involute splines.

FIG. 5 schematically illustrates, by way of non-limitative example, thepivot connection between the two plates (mobile and variableinclination). FIG. 5 is a sectional view along a plane comprising theaxis of drive shaft 5. This figure shows variable-inclination plate 7,mobile plate 2 and connecting rods 8. Rods 8 are in spherical jointconnection in mobile plate 2 without friction pads.

Axis YY is the axis of variable-inclination plate 7. Mobile plate 2 isin pivot connection on variable-inclination plate 7 about inclinationaxis YY of variable-inclination plate 7. Thus, the inclination of mobileplate 2 is identical to the inclination of variable-inclination plate 7.This pivot connection consists of a conical roller thrust 16 and of aball bearing 18.

Mobile plate 2 comprises two outer shoulders 20 and 22 for arrangingconical roller thrust 16 and ball bearing 18. Shoulder 20 with thesmaller diameter is intended to receive conical roller thrust 16 and itis arranged on the side of mobile plate 2 remote from rods 8.Furthermore, shoulder 22 with the larger diameter is intended to receiveball bearing 18 and it is arranged near the side of mobile plate 2 closeto rods 8.

Besides, variable-inclination plate 7 comprises two inner shoulders 19and 21 for arranging conical roller thrust 16 and ball bearing 18.Shoulder 19 with the smaller diameter is intended to receive conicalroller thrust 16 and it is arranged near the center ofvariable-inclination plate 7. Furthermore, shoulder 21 with the largerdiameter is intended to receive ball bearing 18 and it is arranged onthe side of variable-inclination plate 7 close to mobile plate 2.

FIG. 5 further illustrates the device for forming a pin spherical joint10. This device 10 is in accordance with the device for forming a pinspherical joint illustrated in FIG. 4. Device 10 is mounted on driveshaft 5 by means of a key 17.

The invention also relates to the use of the pump according to theinvention for a drilling operation, in particular for injecting drillingmud into a wellbore. Indeed, the pump according to the invention is wellsuited for this use due to its flexibility, compactness and highpressure strength.

For example, the pump according to the invention can be sized to operateup to pressures of the order of 1500 bar, i.e. 150 MPa. Besides, thepump according to the invention can be sized to operate at flow ratesranging from 30 to 600 m³/h.

1. A barrel pump comprising a casing and comprising, within the casing:a drive shaft, a cylinder block comprising at least twocircumferentially distributed compression chambers, the cylinder blockbeing driven by the drive shaft, a mobile plate, at least two pistons intranslation respectively in the compression chambers of the cylinderblock, the pistons being driven by the mobile plate by means ofconnecting rods, wherein in that the mobile plate is driven by the driveshaft and the barrel pump comprises a plate with variable inclinationrelative to the drive shaft, the mobile plate being in pivot connectionrelative to the variable-inclination plate about axis of thevariable-inclination plate.
 2. A pump as claimed in claim 1, wherein thepivot connection between the mobile plate and the variable-inclinationplate consists of means for supporting the loads and means for holdingup the assembly of the two plates.
 3. A pump as claimed in claim 2,wherein the pivot connection between the mobile plate and thevariable-inclination plate consists of a conical roller thrust and of aball bearing.
 4. A pump as claimed in claim 3, wherein the conicalroller thrust is arranged between an outer shoulder of the mobile plateand an inner shoulder of the variable-inclination plate.
 5. A pump asclaimed in claim 3, wherein the ball bearing is arranged between anouter shoulder of the mobile plate and an inner shoulder of thevariable-inclination plate.
 6. A pump as claimed in claim 1, wherein themobile plate is driven by the drive shaft through a pin spherical joint.7. A pump as claimed in claim 6, wherein the pin spherical jointcomprises a device for forming a pin spherical joint in form of a hollowrevolution part comprising a substantially cylindrical inner surface andan outer surface having substantially the shape of a truncated sphere atboth ends, the inner surface comprises at least one groove or one femalespline, and the outer surface comprises at least one crowned spline. 8.A pump as claimed in claim 7, wherein device for forming a pin sphericaljoint is mounted on the drive shaft by means of a key or a splinedshaft, and the mobile plate is mounted on the device by means of atleast one groove cooperating with the at least one crowned spline.
 9. Apump as claimed in claim 6, wherein the mobile plate comprises a partlyspherical inner surface.
 10. A pump as claimed in claim 1, wherein thebarrel pump comprises a means for controlling the inclination of thevariable-inclination plate.
 11. A pump as claimed in claim 10, whereinthe inclination control means comprises a worm drive system.
 12. A pumpas claimed in claim 1, wherein the are connected to the mobile platewithout friction pads.
 13. Use of the barrel pump as claimed in claim 1for a drilling operation, in particular for injecting drilling mud intoa wellbore.
 14. A method for conducting a drilling operation, comprisinginjecting drilling mud into a wellbore using the barrel pump as claimedin claim 1.